"A person acting as a member of the operating crew of an aircraft, or carried in the aircraft for the purpose of so acting, shall not, while so acting or carried, be in a state in which, by reason of his or her having consumed, used, or absorbed any alcoholic liquor, drug, pharmaceutical or medicinal preparation or other substance, his or her capacity so to act is impaired."
However the ONLY person who can accurately judge whether or not the capacity of the operator is impaired is the pilot HIM/HERSELF! And if his/her judgement is ALREADY affected, how can he then assess himself accurately?
According to the Regulations, Capt XX has been compliant - he mightn't FEEL too well, but he's LEGAL!
Whereas Capt MM (who had 1 glass of white wine 7 1/2 hours prior to flight) is suffering NO effects, but is ILLEGAL!
Neither of them consider their "capacity to act" is impaired - which in MM's case we (as outsiders) would probably concur is correct - and in XX's scenario we would GUESS is wrong.
Perhaps the regulations need a tune up so that they are more specific wrt to the amount of ALCOHOL consumed, eg. "..no MORE than 120mls of spirits, liquers, or fortified wines, or 1400mls of beer, or 1000mls of table wine, consumed within the 10 hours immediately preceding a flight and no alcohol to have been consumed in within 8 hours preceding planned departure.